Potential for significant increases to both stratabound and vein type mineralization exists throughout the property. Drilling in Zone 3 has so far been restricted by topography and drilling depth. The furthest hole to the north on the mineral resource (hole PC-95-125) intercepted identical vein type mineralization in the same stratigraphic/structural setting as seen in the underground workings, indicating the vein is still open-ended and continuing to the north. Furthermore, the trend of the vein directly intersects the Rico Showing, where a vein type occurrence has been exposed at surface in bedrock four kilometres north of the last drill hole. This zone also has excellent potential for hosting further stratabound type mineralization.
The southern part of the property contains numerous exposures of vein type material in identical geological settings to that found in the Main Zone. Some wide spaced exploration drill holes have also returned stratabound type mineralization over 3 kilometres south of the defined mineral resource. These mineral showings ("Zones") are approximately 1 kilometre apart and extend approximately 10 kilometres to the south from the Main Zone 3 (at the minesite) to Zone 12.Associated stratabound mineralization has the potential to significantly increase the throughput of the mill, due to its much higher tonnes per vertical meter of depth.
In 2011, CZN completed 26 holes totalling 3,125 metres testing for shallow vein and stratabound mineralization in the immediate mine area and 2,513 metres of coring in four holes approximately 1.5 kilometres north of the mineral resources searching for deeper vein mineralization. Both programs were successful in intersecting mineralization and results from this drilling was reported in press releases date October 3, 2011, November 16, 2011 and February 29, 2012.
Drilling around the Mine Site and north of the existing resources continued in 2012 and results from the 12-hole, 5,629 metre program were announced on November 22, 2012. This program included a 1.3 metre intercept that assayed 2,059 g/t Ag, the highest grade silver intercept from a drill hole from the property, as well as key intercepts from the Mine Site area and the Casket Creek deep target area.
On December 9, 2013, results from an exploration drill program to test a multi-stacked gravity and electromagnetic geophysical anomaly as well as an exploratory program near the mill were reported. The program, which was comprised of five holes totaling 1,472 metres was succesful in that 2 holes to test the geophysical anomaly intersected projections of the Main Quartz Vein and Stockwork mineralization. The exploratory drill program near the mill also intersected Stratabound and Vein mineralization.
The results from the previous programs were incorporated into a 2015 mineral resource update.
Beginning in 2014, Canadian Zinc initiated an underground diamond drill program at the Prairie Creek Mine with the objective of converting part of the currently Inferred Resource to an Indicated category. The drill program is expected to be completed later in 2015 and could result in further upgrades to the resources. These revised resources will be included in an updated mine plan to be incorporated in an update preliminary feasibility study.
The mining contract for the initial underground exploration and development program at the Prairie Creek Mine was awarded to Procon Mining and Tunneling Ltd. in October 2014.
The mining contract was awarded to Procon following a tendering process which included a number of major mining contractors with the objective of optimising mine development and operating costs related to the Prairie Creek Mine. This involved the creation of a comprehensive mine tender package and an underground site visit to Prairie Creek by all prospective contractors, which led to tenders being developed by the contractors and bids submitted which were subsequently assessed by the Company.
The Prairie Creek Mine exploration and development program has been divided into stages.
The first stage was to re-open access to the underground by dewatering and re-installing electrical and ventilation services to the 650 metre-long decline which is located at the end of the 870m underground level. Rehabilitation of the underground workings near the 930m level portal area was completed by removing all old timbers and bolting and shotcreting the area. The portal area at the 930m level also contains the primary ventilation fan which distributes air to the lower level. Further rehabilitation of some manway raises and refuge stations is also planned.
After completion of the rehabilitation stage, Canadian Zinc began an exploration diamond drill program from underground drill stations located at the end of the decline, with the objective of upgrading part of the currently inferred resources to an indicated category. The drilling is planned on four, 50-metre sections and will comprise about 6,000 metres of diamond drill coring. To date, six holes of a proposed 21 hole program have been completed.
In preparation for Procon’s winter underground exploration program, a diesel airlift was completed utilizing the DHC-5 Buffalo aircraft to bring in approximately 200,000 litres of diesel fuel to support operations. A subsequent airlift of mining equipment and supplies using the same aircraft was also completed.
During dewatering of the decline hydrological monitors were installed in the 870m level bedrock walls to measure groundwater aquifer flows. Data from this monitoring program will provide necessary information to predict future underground water pumping requirements and plan water management.
At the same time as the underground program is proceeding, upgrades and repairs of existing surface facilities will continue. This surface program includes completing further site testing and engineering design work for the proposed water storage pond and the waste rock pile, including conducting penetrometer tests on the pond substrate, and additional test pitting in the base area of the proposed waste rock pile facility.
By July 2015, the Company had completed the underground exploration drill program. The 21-hole, 5,484 metre program was carried out from three, 50-metre spaced underground drill stations on the decline from the end of the 870 metre level. All assay results have been received and the detailed interpretation of the results and findings are being compiled and modelled. Preliminary highlights of this program include:
- A previously unknown quartz vein fault structure was discovered in the footwall of the Massive Quartz Vein (MQV). This second vein has been intersected in five holes and appears to be defining a structural transition zone which offsets the general trend of the upper part of the MQV.
- Hole PCU-15-65, first intersected the MQV grading 4.9% Pb, 22.7% Zn and 164 g/t Ag across 1.2m. It then intersected multiple intercepts of Stockwork (STK) mineralization, one which graded 24.7% Pb, 32.7% Zn and 311 g/t Ag across 2.4m, and further down another graded 9.5% Pb, 38.1% Zn and 381 g/t Ag across 1.5m. That same hole intersected the new second quartz vein grading 4.6% Pb, 13.8% Zn and 92 g/t Ag across 2.9m.
- Hole PCU-15-72, the most northern hole drilled in this program, returned substantial MQV mineralization including 17.8% Pb, 33.7% Zn and 247 g/t Ag over 7.5m and an additional intersection of STK mineralization, which graded 6.9% Pb, 12.0% Zn and 116 g/t Ag over 24.5m, and the intersectuion of the second vein which graded 5.6% Pb, 3.8% Zn and 88 g/t Ag over 4,.5m.
- Numerous holes intersected extensions to the previously known STK zone, which occurs mostly outside, but adjacent to, the calculated Indivcated Resource, These intersections will add to the STK resource and this drilling has indicated areas within this resource of significant grades and widths that could be targeted for early, selective mining.
- Detailed underground chip sampling of the Northwest Drift in the 870 metre level workings returned composite grades of 5.6% Pb, 14.2% Zn and 119 g/t Ag across a true width of 4.4m along the strike length of 71.8m further demonstrating the potential for early selective mining of the STK minerlization.